SQL Practice Test

Question 1

To delete data from a table, which SQL statement is used?

Accepted Answer

TRUNCATE

Answer

The `TRUNCATE TABLE` statement is used to quickly remove all rows from a table in SQL. It is a Data Definition Language (DDL) command, which makes it faster and more resource-efficient than `DELETE` for emptying an entire table, as it deallocates the data pages rather than logging individual row deletions. While `DELETE` can also remove data, `TRUNCATE` is specifically for mass deletion of all rows.

Question 2

To update data in a database, which SQL statement is used?

Accepted Answer

UPDATE

Answer

The `UPDATE` statement in SQL is specifically designed to modify existing records within a database table. It allows you to change the values of one or more columns for rows that meet a specified condition. This is the standard and correct SQL command for performing data modifications.

Question 3

How do you select all of the columns from the "Persons" table in SQL?

Accepted Answer

SELECT * FROM Persons

Answer

In SQL, the asterisk (`*`) serves as a wildcard character, signifying 'all columns.' Therefore, `SELECT * FROM Persons` is the correct syntax to retrieve every column and all rows of data from the table named 'Persons.' This command provides a complete view of the table's contents.

Question 4

How do you get a column called "FirstName" from a table called "Persons" in SQL?

Accepted Answer

SELECT FirstName FROM Persons

Answer

To retrieve specific columns from a table in SQL, you list the desired column names directly after the `SELECT` keyword. `SELECT FirstName FROM Persons` explicitly requests only the data from the 'FirstName' column within the 'Persons' table. This allows for targeted data extraction.

Question 5

To extract data from a database, which SQL statement is used?

Accepted Answer

SELECT

Answer

The `SELECT` statement is the fundamental SQL command used to retrieve or extract data from one or more tables in a database. It allows users to specify which columns and rows they want to query, making it the primary tool for data retrieval operations. Other options like `EXTRACT` or `GET` are not standard SQL commands for this purpose.